Resolution of coupling order and station level constraints in train unit scheduling

Train unit scheduling assigns vehicles to cover all trips of a fixed timetable satisfying constraints such as seat demands. With a two-phase approach, this problem is first solved in Phase I as an integer multi-commodity flow problem. Train stations are simplified as single points and coupling orders of train units are left undetermined. In this paper, platforms and their layouts at the stations are restored to complete a fully operable schedule, defined as Phase II. An adaptive approach expanding Phase I to Phase II is proposed. The logistics of (de-)coupling operations, coupling orders and re-platforming are determined in detail to prevent unit blockage where possible, particularly focusing on developing a schedule with conflict-free coupling orders. If unresolvable station level conflicts still exist, the process loops back to Phase I with addressed Phase II constraints to avoid identified conflicts. Thus, the schedule is iteratively improved until it is fully operable.